Conventionally, electrons generated by an electron microscope or an electron beam generator hit a sample where they either induce the reflection of the electron or the emission of secondary electrons. All electrons can be detected by a conventional micro-channel plate detector (MCP), a secondary electron (SE) detector or a semi-conductor detector. When electrons enter these detectors (system) the number of electrons is multiplied through their own structure. For such amplification, a some voltage is applied to a detector or a potential difference generated due to their structure and material is produced. The electric current generated by the electrons undergoing the procedure in above-described detector is amplified by an external amplification circuit.
Referring to FIG. 1, an electron beam B emitted from an electron beam generator 100 is projected onto a sample. A conventional detector 10 detects electrons 9 either from the collision of the electron beam B with the sample or secondary electrons emitted from the sample. The electrons 9 are emitted or bounced from the sample—as indicated by arrows and dots—and are then detected by the detector 10.
However a conventional detector 10 uses a method for performing amplification to collect data using electrons resulting from the collision of the electron beam with the sample or secondary electrons. The number of electrons resulting from the collision of the electron beam B with the sample and the number of secondary electrons, generated by a conventional electron beam generator, is small. The electric current from these detected electrons has to be amplified before usage. In an electron beam generator such as an electron microscope with high energy or a conventional electron beam generator with low energy typical value for the electric current range from Pico ampere to more than hundreds of Pico amperes depending on the application conditions. Therefore, such a detector (detecting system) is configured to immediately multiply the number of collected electrons. For example, a Micro Channel Plate (MCP) or a Back Scattering Electron Detector (BSED) using a P-N junction has been used.
The recent development of an electron beam emission source, such as a micro-column, generates an electron beam with a much higher current at low energy. The number of electrons reaching and interacting with the sample is in the range from hundreds of Pico amperes to Nanoamperes. Compared to a conventional electron column these currents can easily be detected.